Light emitting diode with direct view optic

ABSTRACT

An LED and light guide assembly has an LED with an output surface; a first power input lead electrically coupled to a first pole and having a first surface and a second surface; and a second power input lead electrically coupled to a second pole and having a first surface and a second surface. A unitary, molded light guide has an axially extending, light transmissive body with a light output window. An input window is formed with the unitary, molded light guide being aligned in a zero-gap relationship to capture substantially all the light emitted by the LED. A support is formed integral with the light guide and envelopes a portion of the first surface and the second surface of the first power input lead and the first surface and the second surface of the second power input lead to anchor the guide with respect to the power inputs.

TECHNICAL FIELD

This invention relates generally to light sources and more particularlyto light emitting diode (LED) light sources. Still more particularly, itrelates to LED light sources integrally combined with light guides.

BACKGROUND ART

LEDs have frequently been employed with various light modifying mediasuch as optic fibers and light guides to direct, amplify or otherwiseposition the light output from the LED. The major problem that occurs insuch constructions is the loss of light that is occasioned between theoutput surface of the LED and the input surface of the light modifyingmedia. Even employing the best available optical binding agents and gelsdoes not eliminate this loss effect. Therefore, it would be an advancein the art if this light loss could be eliminated or substantiallyreduced.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of this invention to obviate thedisadvantages of the prior art.

It is another object of the invention to enhance the light output ofLED-light guide combinations.

These objects are accomplished, in one aspect of the invention, by anLED and light guide assembly, comprising: an LED with an output surface;a first power input lead electrically coupled to a first pole of the LEDand having a first surface and a second surface, a second power inputlead electrically coupled to a second pole of the LED and having a firstsurface and a second surface; a unitary, molded light guide having anaxially extending, light transmissive guide body with an internallyreflective surface, the guide body having a light output window; aninput window formed with the unitary, molded light guide being alignedto capture substantially all the light emitted by the LED at the outputsurface; and a support integral with the light guide and enveloping atleast a portion of the first surface and the second surface of the firstpower input lead and the first surface and the second surface of thesecond power input lead to anchor the guide body with respect to thepower inputs.

This construction couples the light guide to the output surface of theLED in a zero-gap relationship insuring that substantially all of thelight emitted by the LED enters the input window of the light guide.Additionally, the integral formation of the support with the light guideinsures that this alignment will be maintained when the assembly ismounted upon a printed circuit board or other substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged, diagrammatic, sectional view of an embodiment ofthe invention;

FIG. 2 is an enlarged, diagrammatic, sectional view of an alternateembodiment of the invention;

FIG. 3 is a circuit diagram of an embodiment of the invention; and

FIG. 4 is a flow diagram of the steps in carrying out an embodiment ofthe invention.

FIG. 5 is an enlarged plan view of the peripheral barbs.

BEST MODE FOR CARRYING OUT THE INVENTION

For a better understanding of the present invention, together with otherand further objects, advantages and capabilities thereof, reference ismade to the following disclosure and appended claims taken inconjunction with the above-described drawings.

Referring now to the drawings with greater particularity, there is shownin FIG. 1 an LED and light guide assembly 10, comprising: an LED 12 withan output surface 14. A first power input lead 16 is electricallycoupled to a first pole 18 of the LED 12. The first power input lead 16has a first surface 16 a and a second surface 16 b. A second power inputlead 20 is electrically coupled to a second pole 22 of the LED 12, forexample, by a wire 23, and has a first surface 20 a and a second surface20 b. The power input leads 16 and 20 are preferably formed from amaterial having a high thermal conductivity since they can function alsoas a heat sink. While many materials can thus qualify, fabrication ofthe power input leads from a copper alloy is preferred. After formationof the input power leads they can be coated or plated to eliminateoxidation and have the requisite electrical contact pads applied toreceive the LED chip and wire bonds.

A unitary, molded light guide 24 cooperates with the LED 12 and has anaxially extending, light transmissive guide body 26, using totalinternal reflection to guide and redirect the light with a light outputwindow 28. An input window 30 is formed with the unitary, molded lightguide 24 and is aligned in a zero light gap relationship with the LED 12to capture substantially all the light emitted from the top and sidesurfaces of the LED 12 at the output surface 14. A support 32 isintegral with the light guide 24 and envelopes at least a portion of thefirst surface 16 a and the second surface 16 b of the first power inputlead 16 and the first surface 20 a and the second surface 20 b of thesecond power input lead 20 to anchor the guide body with respect to saidpower input leads 16 and 20. Preferably the light guide body 26 isformed as a complex parabolic concentrator, as described in co-pendingpatent application Ser. No. 11/443,833, filed May 31, 2005, which isbase on and claims priority from Provisional Application Ser. No.60/705,744, filed Aug. 5, 2005.

The unitary guide 24 further includes a base 34 with a planar portion 36and a base coupling 38. The first power input lead 16, the second powerinput lead 20 and the base 34 all have portions in a substantiallycommon plane for mutual mounting to a common support 100, which can be aprinted circuit board having conductive solder traces 102 thereon. Thebase coupling 38 is formed to frictionally engage a recess 110 insupport 100 to form an anchor for the LED assembly and preferablyincludes peripheral barbs 38 a (see, FIG. 5) to aid in the frictionalengagement.

In the embodiment shown in FIG. 1 the power input leads 16 and 20include offset projections 17, 21, respectively, to contact theconductive solder traces 102.

To achieve the zero light gap relationship between the output window 14of the LED 12 and the input window 30 of the unitary light guide 24(see, FIG. 1), the process illustrated in FIG. 4 is employed.

That is, the first and second power input leads 16 and 20 are formedwith an electrically isolating region 51 between them. A first pole, forexample 18, of an LED 12 is attached to the first power input lead 16and the second pole 22 of the LED 12 is attached to the second powerlead 20, for example, via a gold wire 23 to form a subassembly 50.

The subassembly 50 is then fed into a mold and an optically clear,transparent epoxy molding compound is applied into the mold at alow-pressure fill rate to maintain the integrity of the wire bond and toform the unitary LED light guide assembly 10. A preferred opticallyclear compound is HYSOL® MG97 available from LOCTITE Corporation.

This process of molding the light guide input to integrally envelope theLED insures a zero-light gap relationship between the output surface 14of the LED 12 and the input window 30 of the light guide 24. Therelationship is fixed and is not subject to misalignment duringsubsequent handling. The integral support 32 encompasses both the upperand lower surfaces of the power input leads to further maintainalignment and the integral base 34 and base coupling 38 insure properengagement with the printed circuit board.

An alternate embodiment of the invention is shown in FIG. 2 whereinpower input leads 16 c and 20 c are formed as planar members. As shownin FIG. 2 (and applicable to the embodiment of FIG. 1) multipleapertures 60 can be formed in the power input leads to allow penetrationof the epoxy molding compound to further secure leads into a unit.

After being mounted to a substrate such as a printed circuit board, theunit can be sent through a solder re-flow process to secure electricallyand mechanically the unit to the substrate.

There is thus provided an LED and light guide assembly that provides azero-gap lighting relationship between the LED chip and the light guidethat passes all or substantially all of the LED-emitted light. Alignmentis maintained through all subsequent handling because of the unitaryconstruction,

While there have been shown and described what are at present consideredto be the preferred embodiments of the invention, it will be apparent tothose skilled in the art that various changes and modifications can bemade herein without departing from the scope of the invention as definedby the appended claims.

1. An LED and light guide assembly, comprising: an LED with an outputsurface; a first power input lead electrically coupled to a first poleof said LED and having a first surface and a second surface; a secondpower input lead electrically coupled to a second pole of said LED andhaving a first surface and a second surface; a unitary, molded lightguide having an axially extending, light transmissive guide body with aninternally reflective surface, said guide body having a light outputwindow; an input window formed with said unitary, molded light guidebeing aligned to capture substantially all the light emitted by the LEDat said output surface; and a support integral with said light guide andenveloping at least a portion of said first surface and said secondsurface of said first power input lead and said first surface and saidsecond surface of said second power input lead to anchor the guide bodywith respect to said power inputs.
 2. The LED and light guide assemblyof claim 1, wherein said unitary guide further includes a base havingplanar portion, said first power input lead, said second power inputlead and said base all having portions in a substantially common planefor mutual mounting to a common support.
 3. The LED and light guideassembly of claim 1, wherein said unitary guide includes a base couplingformed to frictionally engage a recess in said support to form an anchorfor the LED assembly.
 4. The LED and light guide assembly of claim 1,wherein said LED is coupled to said light guide in a zero light-gaprelationship.
 5. A unitary LED and light guide assembly comprising:first and second electrically isolated power input leads; an LED havinga light output surface, electrically connected between said first andsecond power input leads; and a unitary, molded light guide having anaxially extending, light transmissive guide body with an internallyreflective surface, said guide body having a light output window and aninput window formed with said unitary, molded light guide, said inputwindow being aligned to capture substantially all the light emitted bythe LED at said output surface; said unitary light guide including upperand lower portions that maintain said electrical isolation between saidfirst and second power input leads.
 6. A method of making a unitary LEDand light guide assembly comprising the steps of: forming first andsecond electrically isolated power input leads; securing an LED with anoutput surface to one of said first and second electrically isolatedpower input leads; electrically connecting said LED to the other of saidelectrically isolated power input leads to form a subassembly; placingsaid subassembly in a mold; and molding a unitary light guide about saidsubassembly.
 7. The method of claim 6, further including the steps ofproviding said unitary light guide with an axially extending, lighttransmissive guide body with an internally reflective surface, saidguide body having a light output window, an input window formed tocapture substantially all the light emitted by the LED at said outputsurface; and molding the unitary light guide about said subassembly toprovide an integral support enveloping at least a portion of a firstsurface and a second surface of said first power input lead and a firstsurface and a second surface of said second power input lead to anchorsaid guide body with respect to the electrically isolated power inputs.